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Chap 9

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o1234567889q's version from 2017-12-11 23:03

Section

Question Answer
which rule to use when drawing lewis dot symbolshund's rule
oxide chemical formulaO^-2
aluminum fluorideAlF3 (aluminum charge is +3 and fl is -1 so crisscross)
How many valence electrons does He have2 (not 8)
The lattice energy is the energy required toseparate the ions in 1 mole of a solid ionic compound into gaseous ions
Lattice energy (E) increases as Qincreases and/or as r decreases
lattice energy equationE=K *( (Q+ * Q-)/r )
what do the letters in E=K *( (Q+Q-)/r ) meanQ+ and Q- are the charges on the ions, k is a proportionality constant, and r is the distance between the two charges
he Born-Haber cycle allows us tounderstand and determine the lattice energies of ionic solids
lattice energy values are usually expressed with the unitskJ/mol
Ionization Energy isthe energy required to remove an electron from a neutral atom or an ion
In general, ionization energy increasesacross the periodic table from left to right and bottom to top
Electron Affinityis the energy released when an electron is added to a neutral atom or an ion
In general, electron affinity increasesfrom left to right across the periodic table and bottom to top
what to do w/ electron affinity when calculating lattice energy and whysubtract because energy release is negative
Dissociation energyis the energy required to break apart a compound
Sublimation energyis the energy required to cause a change of phase from solid to gas, bypassing the liquid phase
may also be referred to as the energy of atomizationsublimation energy
The heat of formationis the change in energy when forming a compound from its elements
Hess's Lawstates that the overall change in energy of a process can be determined by breaking the process down into steps, then adding the changes in energy of each step. The Born-Haber Cycle is essentially Hess's Law applied to an ionic solid
The Born-Haber Cycle can be reduced to a single equationLattice energy= Heat of formation- Heat of atomization- Dissociation energy- (sum of Ionization energies)- (sum of Electron Affinities)
MgF2 is composed ofMg(s)+F2(g)
equation for bond energy of F2F2(g)>2F(g)
equation for lattice energy of MgF2Mg^+2(s) + 2F^-(g) > MgF2(s)
equation for enthalpy of sublimation of MgMg(s) > Mg(g)
covalent bonda chemical bond in which two or more electrons are shared by two atoms
Bond LengthsTriple bond < Double Bond < Single Bond
Polar covalent bond or polar bonda covalent bond with greater electron density around one of the two atoms
Electronegativitythe ability of an atom to attract toward itself the electrons in a chemical bond
electron affinity is _ while electronegativity is _measurable (x(g)+e- > x^- (g) ), relative
how electronegativity increases across the periodic tableleft to right and bottom to top
increasing difference in electronegativity in bondscovalent=share e-, polar covalent=partial e- transfer, ionic=transfer e-
a bond is classified as a nonpolar covalent bond when the difference in electronegativity of the atoms that form the bond is between0 to 0.4
a bond is classified as a polar covalent bond when the difference in electronegativity of the atoms that form the bond is between0.4 to 1.7
a bond is classified as an ionic bond when the difference in electronegativity of the atoms that form the bond isgreater or equal to 2.1
The sum of the formal charges of the atoms in a molecule or ion must equalthe charge on the molecule or ion
equation for formal charge(formal charge on an atom in a Lewis structure) = (total number of valence electrons in the free atom) - (total number of nonbonding val electrons) - 1/2(total number of bonding electrons)
resonance structureone of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure
The enthalpy change required to break a particular bond in one mole of gaseous molecules is thebond energy
Bond EnergiesSingle bond < Double bond < Triple bond
memorize